Heat-developable light-sensitive materials

ABSTRACT

A heat-developable light-sensitive material containing no silver halide is provided. An image-forming ability is imparted to the material by activating the heat-developable light-sensitive reproducing material containing at least a silver salt of long chain fatty acid, an organic reducing agent and an organic carboxylic acid by means of a heat pre-treatment.

United States Patent 191' Takegawa et al.

HEAT-DEVELOPABLE LIGHT-SENSITIVE MATERIALS Inventors: Yukio Takegawa;Takao Matui;

' Tetuya Higuchi, all of Tokyo, Japan Assignee: Oriental PhotoIndustrial Co., Ltd.,

Tokyo, Japan Filed: Mar. 22, 1973 Appl. No.: 343,867

Foreign Application Priority Data Mar. 27. l972 Japan 47-30568 US. Cl.96/48 HD, 96/50 PT, 96/67, 96/94 R, 96/114, 96/1 14.] Int. Cl G03c 1/60,G030 l/72 Field of Search 96/l 14.1, 48 HD, 94 R, 96/67, 50 PT PrimaryExaminer-Ronald H. Smith Assistant Examiner-Alfonso T. Suro PicoAttorney, Agent, or FirmWoodhams. Blanchard and Flynn 5 7 ABSTRACT Aheat-developable light-sensitive material containing no silver halide isprovided. An image-forming ability is imparted to the material byactivating the heatdevelopable light-sensitive reproducing materialcontaining at least a silver salt of long chain fatty acid, an organicreducing agent and an organic carboxylic acid by means of a heatpre-treatment.

. 16 Claims, N0 Drawings HEAT-DEVELOPABLE LIGHT SENSITIVE MATERIALSBACKGROUND OF THE INVENTION 1. Field of the Invention The presentinvention relates to a heat-developable light-sensitive material. Moreparticularly, the invention relates to a heat-developablelight-sensitive material containing no silver halide, the sensitivityand image densities of which have been highly improved by subjecting thematerial to a suitable heat pre-treatment.

2. Description of the Prior Art Known silver halide photography issuperior to other various photographic techniques with respect tosensitivity, gradient, etc. However, its treatment steps such asdevelopment and fixing steps are troublesome, since they are carried outin the wet system, and it is inconvenient to mechanize the whole stepsin many aspects.

Many attempts have been made for improving the silver halide photographyby converting its treatment steps from the wet system to the dry system.

Among them, heat-developable light-sensitive materials which are to bedeveloped by heat treatment have been proposed in patent literatures. InJapanese Patent Publication No. 4924/1968 (Belgian Patent No. 663,] 12;French Patent No. 1,441,691; OLS 1,572,203; British Patent No. 1,110,046), there has been disclosed a heat-developable light-sensitivematerial consisting of an organic silver salt, areducing agent and asilver halide catalytically contacted with said organic silver ion. Insaid Japanese Patent Publication No. 4924/1968, there is described anexample as control in which no halogen donor is used. In this example, asystem comprising an organic silver salt, a reducing agent, a binder andan acidic stabilizer is exposed to the pattern of an image and thenheat-developed to obtain only a faint gray image on slight turbid yellowback. It is also described therein that no practically advantageousimage density could be obtained even by changing exposure conditions andheat-developing conditrons.

SUMMARY OF THE INVENTION We have found that a heat-developablelightsensitive material capable of producing an effective image densitycan be obtained by forming a single layer or multilayers containing asilver salt of long chain fatty acid, an organic reducing agent and anorganic carboxylic acid, preferably on a support, and then subjectingthe same to a heat pretreatment under proper heating conditions toimpart an excellent light sensitivity to said material, which can neverbe obtained without such heat pre-treatment.

Although the detailed mechanism of imparting light sensitivity to thesystem not containing light-sensitive silver halide to make theformation of an image of effective image density possible is not yetknown, a possible explanation is as follows:

By the heat pre-treatment according to the present invention, the silversalt of long chain fatty acid which is hardly dissociated at ambienttemperature may be partially thermally dissociated to release silverion. Thus, the resulted silver ion may form a neutral silver aggregatewhich is capable of acting as sensitivity speck in the successiveexposure step. Another possible extate to melt and dissociate the silversalt of long chain fatty acid. The dissociated silver ion forms asensitivity speck according to the above assumed mechanism.

Although the above mechanisms have not been proved yet, it cannot but beconsidered to be a surprising, quite important finding that a silversalt of long chain fatty acid which has been considered to benonsensitive or practically non-sensitive can be converted to a usefullight-sensitive material by the heat pretreatment according to thepresent invention.

Description will be made on the process for the preparation of theheat-developable light-sensitive materials of the present invention andthe process for the formation of an image in said materials.

According to a preferred embodiment of the present invention, the firstcoating layer comprising a silver salt of long chain fatty acid and anorganic carboxylic acid dispersed in a binder material is provided on asupport made of such materials as paper, etc. Then, the surface of thelayer is treated with a treating solution containing a reducing agentand thereafter dried. However, at this step, the product hardly has anyimage-forming property. Then, it is subjected to a heat pre-treatmentfor a proper time at a temperature, at which a part of the silver saltin the system may be dissociated. Thus, an excellent light sensitivityis obtained. The lightsensitive material thus obtained is exposed to thepattern of an image and then heat-developed at a temperature higher thanthat of the heat pre-treatment. By this treatment, a silver image isformed selectively in the exposed portion by the action of the reducingagent contained therein. As the energy source for the exposure,ultraviolet rays or another radiation energy may be used in addition tovisible rays.

As clearly shown by the above described process for the preparation andprocess for the formation of an image, the light-sensitive material ofthe present invention hardly has light-sensitivity before the heatpretreatment and, therefore, it may be exposed to ordinary indoor lightsfor a short time. Further, by adding mercury salts which will bedescribed below as antifoggant, the light-sensitivity prior to the heatpretreatment can be inhibited completely. Namely, no particularlight-intercepting means is required at the time of packing, storage ortransportation, if the material is passed through a heating roll orsubjected to another heat pre-treatment immediately before the materialis to be introduced in a successive exposure device.

The sensitivity imparted to the material by the heat pre-treatment isnot substantially extinguished as time elapses. This property is utterlydifferent from the phenomenon that the sensitivity caused by theelectric charge extinguishes as time elapses in electrophotography.However, the sensitivity is inclined to be gradually extinguished if thematerial is placed in an atmosphere containing vapor of a solvent whichis capable of swelling and dissolving the coated material. Therefore,for preventing the reduction of the sensitivity, it is preferred toavoid the use of atmosphere of a solvent such as trichloroethylene,toluene, acetone and alcohol. On the contrary, for promoting thereduction of sensitivity intentionally, the material may be exposed tothe atmosphere of such solvents.

As silver salts used in the present invention, there may be mentionedsilver salts of organic acids or silver salts of organic compoundscontaining imide group or mercapto group. Particularly, those which arehardly deteriorated or darkened at room temperature under indoor lightare silver salts of long chainfatty acids such as silver behenate,silver stearate, silver palmitate, silver myristate, silver laurate.silver oleate and silver hydroxystearate. Silver salts of fatty acidshaving 18 24 carbon atoms arepreferable.

As reducing agents used in the present invention, there may be mentionedaromatic compounds substituted with hydroxyl group- Particularlyeffective compounds are hydroquinone, methylhydroquinone,chlorohydroquinone, bromohydroquinone, catechol, pyrogallol,methylhydroxynaphthalene, aminophenol, 2,2-methylene-bis(6-tert.-butyl-4-methylphenol), 4,4-butylidene-bis(6-tert.-butyl-3-methylphenol),4,4-thiobis-(6-tert.-butyl-2-methylphenol), etc. Furthermore, aminocompounds such as N,N"-diethyl-pphenylenediamine andN-phenyl-N"-isopropyl-pphenylenediamine are also effective. In addition,bisnaphthol reducing compounds described in U.S; Pat. No. 3,672,904(French Patent No. 2,090,923; Belgian Patent No. 766,589) are alsoeffective. Those compounds may be used singly or in combination.

Suitable organic carboxylic acids used in the present invention arealiphatic monocarboxylic acids, aliphatic unsaturated monocarboxylicacids, dicarboxylicacids and aromatic carboxylic acids. There may bementioned, for example, capric acid, lauric'acid, palmitic acid, stearicacid, arachidic acid, behenic acid, lignoceric acid, cerotic acid,linolic acid, oleic acid, succinic acid, adipic acid, sebacic acid,benzoic acid, cinnamic acid, salicyclic acid, 'p-hydroxybenzoic acid,2,6- dihydroxybenzoic acid, phthalic acid, isophthalic acid, trimelliticacid, pyromellitic acid, diphenic acid, 5,5 -methylene-bis-salicyclicacid, tetrachlorobenzoic acid and-tetrabromobenzoic acid. Particularly,long chain fatty acids having 18 to 24 carbon atoms are preferable.

Optimum temperature range and heating time of the heat pre-treatmentwhich is one of characteristic fea tures of the present invention dependon the kinds of silver salt of long chain fatty acid, organic reducingagent and organic carboxylic acid used. In this heat pre-treatment, itis desirable that as much as the amount of heat should be supplied tothe material within the limit of substantially causing no fog on thematerial, that is, the change in optical density of the surface of thematerial during the heat-pre-treatment being less than 0.]. Generally,the heat treatment can be carried out at a temperature of 50 200C.Preferably, the heat pretreatment should be effected at 70 120C for ashort period of time. For example, when a system comprising acombination of silver behenate,

with a heatingroll, heating plate or hot air at the time of drying or ata suitable time after the drying but before the exposure.

The light-sensitive material of the present invention may be added witha toning agent, anantifoggant etc., depending upon the kinds of silversalt or reducing agent used. For example, phthalazinone and derivatesthereof described astoning agents for heat sensitive reproducing papercontaining a silver salt of long chain fatty acid in US. Pat.No..3,080,254 are effective toning agents. Further, cyclic imidesdisclosed in U.S. Pat. No. 3,672,904 .are also effective toning agents.Mercury salts described in US. Pat. No. 3,589,903 are effective asantifoggant, storage stabilizer and toning agent. White pigments such aszinc oxide, titanium dioxide, etc. have effects of improving whitenessof the back (non-image part) and also of improving image density andapparent sensitivity.

The light-sensitive material of the present invention can be sensitizedby incorporating therein a spectral sensitizing dye selected from theclass consisting of cyanines, merocyanines oxonols and acridines. Thoughit is said that Acridine Yellow have nosensitizing effect to silverhalides, it can also be used in the present invention.

A binder may be preferably incorporated in the lightsensitive materialof the present invention.

As suitable binders, there may be metioned polyvinyl butyral, celluloseacetate butyrate, polymethyl methacrylate, polyvinyl pyrrolidone,ethylcellulose, cellulose acetate, cellulose acetate butyrate, polyvinylacetate, polyvinyl alcohol and. gelatin.

In preparing the light-sensitive material of the present invention,there is preferably used'a support or a base. Any material which isstable against heating may be used. Suitable supports or bases are filmsof synthetic resins such as polyethylene terephthalate, poly- 1carbonate and cellulose acetate; foils of metals such as2,2-methylene-bis(6-tert.-butyl-4-methylphenol) and behenic acid isemployed as in Example 3 which will be given below,-it is preferred tocarry out the heat treatment at 80C for 5 3.0 seconds or at 100C for l a5 seconds. Heating for a longer period of time is undesirable, since itcauses fog.

A preferred heat pre-treatment comprises heating the surface of asupport which was coated with a dispersion of a silver salt of longchain fatty acid and an organic carboxylic acid in a suitable binder andtreated with a solution of a reducing agent in a suitable solvent,

aluminum; and various kinds of papers.

Optimum ratio of the components of the present invention depends uponthe kinds of silver salt of long chain fatty acid, reducing agent andorganic carboxylic acid used. In general, it is proper to use 10 0.01part by weight of an organic reducing agent and 10 0.01 part by weightof an organic carboxylic acid per 1 part by weight of a silver salt oflong chain fatty acid. Preferably, l l/10 mole of an organic reducingagent and 10 l/l0 mole of an organic carboxylic acid are used per moleof a silver salt of long chain fatty acid.

It will be easily understood by those skilled in the art that in placeof the heat-pre-treatment of the above coating composition, a selectiveheat image may be applied followed by the whole surface exposure andheat development for .the purpose of heat-sensitive reproduction. Thepresent invention will now be illustrated by way of examples.

Example 1 Silver behenate 17 g -Continued Behenic acid 13 g Polyvinylbutyral 40 g Heat pre- Density Tolu 350 l Sample treatment SensitivityDm Df Dm-Df Ethanol 350 ml 5 N0. temperature l 0.08 0.08 Then, thesecond coating solution containing a re- 2g 8-32 8-82 8 ducing agent ofthe following composition was applied 4 s0 7 liOO 0:08 0:92 by using aroll coater and dried at a temperature below 10 5 H 50C. Amount of thecoating was 1.0 g per m of the base after drying.

Hydroquinone 30 g Polyvinyl butyral 10 g Methanol 1000 ml The thusresulting coating composition was subjected to heat pre-treatment with aheating roller at 90C for 5 seconds and then exposed to the light ofblue luminescent lamp (Toshiba FL-B) through a negative image. Then, itwas heated for development at 105C for 5 seconds to obtain a dark brownpositive image.

Example 2 Coating compositions were prepared in the same manner as inExample 1, except using an equimolar amount of sebacic acid in place ofbehenic acid and 23 g of N-phenyl-N-isoprop yl-p-phenylene-diamine inplace of hydroquinone reducing agent in the second coating liquid. Thesecoating compositions were applied to the same base paper in the samemanner as in Example 1. After heat pre-treatment, exposure and heatdevelopment in the same manner as in Example 1, a dark brown positiveimage was obtained. Suitable heating conditions of the heatpre-treatment and heat development in this case were 80C for 5 secondsand and 100C for 5 seconds, respectively.

EXAMPLE 3' A heat developable light-sensitive material was prepared inthe same manner as in Example 1, except that the second coating solutionof the following composition was used. The amount of the coating was 2.5g per m of the base after drying.

2,2'-methylenc-bis(6-tert.-butyl-4-methylphenol) 100 g Phthulazinone 5 gPolyvinyl butyral l0 g Methanol l000 ml Sensitivity is represented bynumber ofsleps of tablet which gives a density of0,l above the fog. "Dmand Df represent the image maximum density and fog density.respectively.

EXAMPLE 4 The first coating dispersion and the second coating solutionof the following compositions were applied to a photographic base paperin this order and then dried.

First coating dispersion:

Silver stearate 15 g Stearic acid ll g Polyvinyl butyral 20 g Toluene300 ml Ethanol 300 ml Second coating solution:

2,2-methylene-bis(o-tert-butylA-methylphenol) Phthalazinone 5 gPolyvinyl butyral 10 g Methanol i000 ml The thus obtained coated paperwas subjected to heat pre-treatment at C for 15 seconds by contactingthe back surface thereof with a heating plate. Then, a negative imagewas printed thereon by using a blue luminescent lamp. After heating at Cfor 5 seconds, a brown positive image was obtained on the white back.

EXAMPLE 5 The first coating dispersion and the second coating solutionof the following compositions were applied to a photographic base paperin this order and then dried.

First coating dispersion:

Silver behenate 17 g Behenic acid l3 g Mercuric acetate 0.12 g Polyvinylbutyral 40 g Toluene 350 ml Ethanol 350 ml Second coating solution:

2,2'-methylene-bis(6-tert.-butyl-4-methylphenol) I00 g Phthalazinone 5 gPolyvinyl butyral 10 g Methanol I000 ml tained, the back being white.The other piece was exposed to the light of 40 W day-light luminescentlamp (Toshiba Flo-40 8D.) to be used for interior illumination at adistance of 2 m for 2 hours prior to the heat pretreatment. Thereafter,heat pre-treatmen't, exposure and heat development were carried out inthe same manner as above. in spite of the above 2 hours exposure, a pureblack image completely free from fog could be obtained.

EXAMPLE 6.

100 Parts of the first coating dispersion used in Example l wereprepared. The following components were added and dissolved theretosuccessively, immediately before the application.

2,2-methylene-bis( 6-tert.-butyl-4-methylphenol) Phthalazinone 0.65 g

The thus resulting coating solution was applied to a photographic basepaper and dried. After heat pretreatment, exposure and heat developmentin the same manner as in the preceding example, a black positive imagecould be obtained.

EXAMPLE 7 The second coating solution in Example was replaced with thefollowing coating composition containing the following spectralsensitizing dye:

Second coating solution:

2,2'-Methylene-bis'(6-tert.-butyl-4-methylphenol) W lOO g Phlhalazinone5 g Acridine Yellow G (Cl-46025) 0.0l g Polyvinyl butyral 10 g MethanolI000 ml EXAMPLE 8 On the surface of the coated paper prepared in thesame manner as in Example 5, the following third coating solutioncontaining a spectral sensitizing dye was applied.

Third coating composition:

l-carboxymethyl-5-[( 3-ethyl-2( l )-benzoxazolidene)-ethylidcne]-3-phcnyl-2-thiohydantoin Methanol I000 ml Afterpre-treatment followed by exposure and then heat development in the samemanner as in Example 7, a black positive image could be obtained.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

8 1. A heat-developable light-sensitive material comprising a silversalt of long chain fatty acid, an organic reducing agent and an organiccarboxylic acid, to which a heat-pretreatment was effected so as toimpart to the material an image-forming ability by activation.

2. A heat-developable light-sensitive material according to claim 1, inwhich said heat-pretreatment was effected at a temperature of 50 to200C.

3. A heat-developable light-sensitive material according to claim 1, inwhich said heat-pretreatment was effected at a temperature of to C andthe change in optical density of the surface of the material during theheat-pretreatment is below 0.1.

4. A heat-developable light-sensitive material according to claim 1, inwhich 10 0.01 part by weight of the organic reducing agent and 10 0.0lpart by weight of the organic carboxylic acid are used based on 1 partby weight of the silver salt of long chain fatty acid.

5. A heat-developable light-sensitive material according to claim 1, inwhich 1 l/l0 mole of the organic reducing agent and 10 l/ 10 mole of theorganic carboxylic acid are'used based on I mole of the silver salt oflong chain fatty acid. v

6. A heat-developable light-sensitive material. according to claim 1, inwhich aspectral sensitizing dye selected from the class consisting ofcyanines, merocyanines, oxonols and acridines is incorporated in thematerial.

7. A heat-developable light-sensitive material according to claim 1, inwhich the silver salt is a silver salt of long chain fatty acid having18 to 24 carbon atoms.

the material.

11. A heat-developable light-sensitive material according to claim 10,in which a layer or layers containing the silver salt, the organicreducing agent, the carboxylic acid and the binder are provided onasupport.

12. A process for the preparation of heatdevelopable light-sensitivematerials which comprises the steps of providing a first coating layercomprising a dispersion of a silver salt of long chain fatty acid and anorganic carboxylic acid on a support, then treating the surface of thelayer with a solution containing an organic reducing agent, drying thesame and subjecting it to a heat pretreatment at a temperature of 50200C in order to dissociate a part of the silver salt.

13. A process for forming an image which comprises the steps of applyinga radiation energy to the material according to claim 1 in a pattern ofthe image for exposure and then heat-developing the same.

14. A reproducing material comprising a silver salt of long chain fattyacid, an organic reducing agent and an organic carboxylic acid which islight inactive before it is subjected to heat-pretreatment.

15. A process for imparting light-sensitivity, in which the materialaccording to claim-l4 is subjected to heat- 9 10 pretreatment to convertthe material to a light-sensitive according to claim 14 in a pattern ofthe image, exposone. ing the whole surface to radiation energy and then16. A process for forming an image which comprises heat-developing thesame. the steps of applying a thermal energy to the material

2. A heat-developable light-sensitive material according to claim 1, inwhich said heat-pretreatment was effected at a temperature of 50* to200*C.
 3. A heat-developable light-sensitive material according to claim1, in which said heat-pretreatment was effected at a temperature of 70*to 120*C and the change in optical density of the surface of thematerial during the heat-pretreatment is below 0.1.
 4. Aheat-developable light-sensitive material according to claim 1, in which10 - 0.01 part by weight of the organic reducing agent and 10 - 0.01part by weight of the organic carboxylic acid are used based on 1 partby weight of the silver salt of long chain fatty acid.
 5. Aheat-developable light-sensitive material according to claim 1, in which1 - 1/10 mole of the organic reducing agent and 10 - 1/10 mole of theorganic carboxylic acid are used based on 1 mole of the silver salt oflong chain fatty acid.
 6. A heat-developable light-sensitive materialaccording to claim 1, in which a spectral sensitizing dye selected fromthe class conSisting of cyanines, merocyanines, oxonols and acridines isincorporated in the material.
 7. A heat-developable light-sensitivematerial according to claim 1, in which the silver salt is a silver saltof long chain fatty acid having 18 to 24 carbon atoms.
 8. Aheat-developable light-sensitive material according to claim 7, in whichsaid silver salt is selected from silver behenate and silver stearate.9. A heat-developable light-sensitive material according to claim 1, inwhich said carboxylic acid is a long chain fatty acid having 18 to 24carbon atoms.
 10. A heat-developable light-sensitive material accordingto claim 1, in which a binder is incorporated in the material.
 11. Aheat-developable light-sensitive material according to claim 10, inwhich a layer or layers containing the silver salt, the organic reducingagent, the carboxylic acid and the binder are provided on a support. 12.A process for the preparation of heat-developable light-sensitivematerials which comprises the steps of providing a first coating layercomprising a dispersion of a silver salt of long chain fatty acid and anorganic carboxylic acid on a support, then treating the surface of thelayer with a solution containing an organic reducing agent, drying thesame and subjecting it to a heat pretreatment at a temperature of 50*-200*C in order to dissociate a part of the silver salt.
 13. A processfor forming an image which comprises the steps of applying a radiationenergy to the material according to claim 1 in a pattern of the imagefor exposure and then heat-developing the same.
 14. A reproducingmaterial comprising a silver salt of long chain fatty acid, an organicreducing agent and an organic carboxylic acid which is light inactivebefore it is subjected to heat-pretreatment.
 15. A process for impartinglight-sensitivity, in which the material according to claim 14 issubjected to heat-pretreatment to convert the material to alight-sensitive one.
 16. A process for forming an image which comprisesthe steps of applying a thermal energy to the material according toclaim 14 in a pattern of the image, exposing the whole surface toradiation energy and then heat-developing the same.